1. Field of the Invention
The present general inventive concept relates to a high voltage power supply (HVPS) that is used in a laser printer or a laser replicator, and more particularly, to a HVPS to prevent abnormal operation, which can occur when power is initially supplied, and where a sudden overshoot phenomenon can occur in an output voltage.
2. Description of the Related Art
A high voltage power supply (HVPS) is a device that receives input voltages (5 [V], 24 [V] or the like) from a switching mode power supply (SMPS) and a main board and generates and outputs high voltages required for forming an image of a transcription process according to a pulse width modulation (PWM) signal of a controller. The HVPS transforms a DC input voltage of 24 [V] into a high voltage in the range of several hundreds to several thousands of volts using a transformer, and outputs the voltage.
FIG. 1 is a circuit view illustrating a conventional HVPS. Referring to FIG. 1, a controller 10 outputs a power signal of 24 [V] and a PWM signal. An input unit 20 converts the PWM signal provided from the controller 10 into a DC voltage using a RC low pass filter. A comparison unit 30 controls output of the power signal of 24 [V] by comparing the DC voltage output signal of the RC low pass filter to a reference voltage signal. A transformation unit 40 converts the output signal of the comparison unit 30 into a transistor driving signal and transforms the converted driving signal into a high voltage type signal. A rectification unit 50 rectifies the high voltage type signal of the transformation unit 40 and finally outputs a high voltage signal of a DC type. The final output high voltage DC signal stabilizes the output of the rectification unit 50 using feedback to the comparison unit 30.
The controller 10 provides the PWM signal using a logic control signal of 5 [V] and the power signal of 24[V] when power is to be supplied to office automation (OA) devices by the HVPS. When the PWM signal provided from the controller 10 does not maintain a logic HIGH state when the power signal of 24 [V] is first input, the PWM signal is instantly detected as a LOW state and a high voltage peak is suddenly generated in a high voltage DC signal output. This phenomenon negatively influences each device in which a HVPS is used to supply power. In particular, when a HVPS is used to supply power in an image forming apparatus, this phenomenon negatively affects the lifetime of a high voltage roller and the formation of an image.